In web-fed printing presses, printing, drying, cooling, forming, folding, and curing operations are often done on a continuous operation machine, feeding in a web of blank paper from a roll and ending with a printed, cut, and folded product. It is often desirable to process the web as quickly as possible, which can contribute to a problem, conventionally referred to as "marking." Marking occurs, for example, when ink that has been printed on the web becomes smeared by downstream processing components such as the angle bars, former board, fan wheel, or other folder or former components. The ink smears when the printed web rubs against downstream components before the ink is sufficiently dry.
Numerous modifications have been attempted to try to solve the problem of ink smearing on press components downstream of the printing units. For example, one such attempt involves using higher viscosity inks so that the inks will not smear as readily as compared to lower viscosity inks. Another attempted solution is to use components with lower friction coefficients in order to prevent the friction force from smearing the ink and raising the temperature of the ink and web. Another attempted solution involves designing the press components and web path so that the normal forces between the web and the components are minimized in order to reduce the likelihood of smearing ink. Additionally, coating the web with silicone has been attempted to reduce friction and thereby reduce web marking. Another attempted solution to the smearing problem includes the use of an air flotation system wherein the web is floated on a cushion of air located between the component and the web, thereby preventing contact of the web and the component.
None of these attempted solutions, however, has adequately solved the problem of ink smearing on press components downstream of the print units. Further, printing presses may also include chill units placed after the dryer unit to lower the temperature of the web and to dry or set the ink. The chill units, however, have limited cooling effect and there is further processing of the web downstream of the chill unit, for example involving wrapping of the web around rollers or angle bars, and over former boards, that produces additional friction and additional heat in the web. In addition, the web is also exposed to room temperature air which contains moisture, which may be absorbed into the web as the web moves through air. Thus, cooling of the web by, for example, a chill unit after drying in an oven is not adequate to minimize the smearing of ink and web marking when a printed web contacts, for example, components of the former section, the angle bars, and other folder components of the printing press downstream of an initial cooling of the web.